An adjustable-rate mortgage is two loans wearing one coat: a fixed-rate loan for an opening stretch of years, then a floating-rate loan for the remainder of the term. Homeowners take one for the opening rate — usually lower than a comparable fixed rate — and meet the second loan only if they still hold the mortgage when the fixed period ends. Many never do: they sell or refinance first. The whole risk and the whole bargain live in three printed numbers — the index, the margin and the caps — and every one of them is in the loan documents before closing, which makes an ARM one of the few mortgage risks that can be read in full in advance.
The name states the schedule: a 5/6 ARM is fixed for the first 5 years, then adjusts every 6 months; a 7/6 is fixed for 7 years, then every 6 months; older loans written as 5/1 or 7/1 adjust once a year after the fixed period. The total term is usually 30 years, so a 5/6 ARM spends 25 of its years adjustable. During the fixed phase the loan behaves exactly like a fixed-rate mortgage — same payment every month, balance falling on its schedule. When the fixed phase ends, the rate is re-set at each scheduled adjustment for the rest of the loan’s life, and the principal-and-interest payment is recalculated each time to retire the remaining balance over the remaining term at the new rate. The payment can rise, fall, or stay — the direction is the market’s, not the lender’s choice.
Every adjustment runs the same formula: new rate = the current value of a public index + the loan’s margin. The index is a benchmark the lender does not control — most conforming ARMs today use the 30-day average SOFR (the Secured Overnight Financing Rate; LIBOR, the older index, was retired in June 2023), and some loans use a Treasury-based index. The margin is a fixed number of percentage points set at closing in the note; it never changes for the life of the loan. Three caps then fence the result, and they are the terms that matter most: an initial adjustment cap limits the first move, a periodic cap limits each later move, and a lifetime cap sets the highest rate the loan can ever carry — often written as a string like 2/1/5 (first adjustment at most 2 points, each later one at most 1, never more than 5 above the start rate) or 5/1/5 on longer fixed periods. A floor, where the note has one, fences the downside the same way. Worst case is therefore a printed number, not a guess: the payment at the lifetime cap can be computed before you sign.
Budget an ARM on its maximum first-adjustment payment, never on its opening payment. If the payment at the first cap would strain the household, the opening discount is being spent on risk, not savings. The loan fits when the plan fits inside the fixed window with room to spare: a likely move, a planned refinance, or income growth that is scheduled rather than hoped for — and it still fits if the exit fails, because the caps define a survivable worst case. The reverse also holds and is stated too rarely: rates fall as well as rise, an adjusted payment can go down, and a borrower who would certainly leave within the fixed period pays fixed-rate prices for certainty they never use. What an ARM is not is a way to afford a larger loan — qualifying at the opening payment while the capped payment breaks the budget is the failure this arithmetic exists to prevent.
Read the ARM rider and the note for the index, the margin, the three caps, any floor, the exact first adjustment date and the adjustment schedule; the Loan Estimate’s adjustable-rate disclosures summarize the same terms, and federal rules require the lender to give you the CFPB’s Consumer Handbook on Adjustable-Rate Mortgages (the CHARM booklet) early in the process. Ask the lender three questions and keep the written answers: what is my rate at the first cap, what is my payment at the lifetime cap, and on what date does my rate first move? File those answers with the closing papers. When an adjustment notice later arrives, check it against the rider — the index value, the margin and the caps — because the servicer’s arithmetic follows the note, and the note is the document you hold.
Homeowner HQ does not set your rate, calculate your adjustment, or service your loan — the rate you pay is the one your note and rider produce, run by your servicer on the schedule printed at closing. What HQ keeps straight is the homeowner’s side of the same loan: the balance on the record against the home’s tracked value, refreshed monthly by your own agent, so the equity position the loan sits on is visible between statements — and when an adjustment changes your payment, the new figure belongs in the same record the month it lands.
Your own agent sends a monthly value update from Homeowner HQ — the estimate, labeled as an estimate, with your equity beside it — and HQ runs on Amazon AWS. For an ARM borrower that record carries one extra date: your first adjustment date, filed with the index, margin and caps from your rider, so the month the payment can move is never a surprise. Read the tracked value against the balance and you can see whether the exit you planned — a sale or a refinance before the fixed period ends — still works at today’s numbers, and when an adjustment notice arrives, file the new payment against the record and correct any fact about the home in HQ with your own agent the same week.
Homeowners are always free. Realtors pay $25/mo to join and lenders join at the $5/mo founding rate, at any book size, with no setup fee; sending messages inside HQ is a $100/mo unlock ($125/mo total for realtors, $105/mo total for lenders). A lender-sponsored realtor joins for $0.
Homeowner HQ is an AI-powered marketing department for agents and lenders — a relationship and revenue engine, not a homeowner database. A homeowner's record routes them back to their own agent; it is never sold and never shown to lenders.